Vacuum belt

ABSTRACT

An improved conveying means for feeding and removing sheet stock to and from a selected area for printing or the like. The conveying means is inexpensively formed from an endless belt of monofilament polyester mesh which moves across a vacuum base disposed beneath a printing head. The mesh functions as a conveying means and is supported by the vacuum base during printing. The mesh size is fine enough to permit the printing of high quality thin paper stock without discernible mesh marks appearing after printing is complete. Vacuum is applied to the underside of the stock to be printed through the mesh from a known type of vacuum base with sufficient force generated to hold the sheet stock properly positioned during printing and feeding. The mesh is of the order of from about 140 to 300 threads per inch. In another embodiment of the invention, the vacuum belt principle is shown in another form wherein it functions as a take-off conveyor which functions to assist in holding the stock during printing. A small manifold functions as a belt guide and is all that is required to pull the stock onto the conveyor.

United States Patent {19] Green et a1.

[ June 26, 1973 VACUUM BELT [73] Assignee: American Screen ProcessEquipment Company, Chicago, Ill.

22 Filed: June 25,1970

21 App]. No.: 49,828

[52] US. Cl 101/287, 271/74 FC, 198/184,

101/126, 226/95, 269/21, 107/382 MV [51] Int. Cl. B411 1/00, B65r 29/24[58] Field of Search 101/126, 287, 382 MV,

10l/ll4,115, 121-124, 407; 271/74, 74 PG, 74 MS, 75,45, 12; 198/184,194; 226/95; 269/21 [56] References Cited UNITED STATES PATENTS2,033,320 3/1936 Belluche 271/45 X 2,606,492 8/1952 Black 101/1243,120,180 2/1964 Black et a1 101/124 2,870,703 l/1959 Balmer 101/1263,598,006 8/1971 Gerber 269/21 3,113,342 12/1963 Halpern et a1. 269/213,453,957 7/1969 Hamilton 269/21 X 3,605,614 9/1971 Gilman et al..101/126 2,866,405 12/1958 Black 101/123 X 3,527,166 9/1970 Jaffa 101/126X 3,199,449 8/1965 Jaffa et a1. 101/126 737,945 9/1903 Lundeberg....101/126 UX 3,477,558 11/1969 Fleischauer... 271/74 MS 3,202,302 8/1965lnsolio 271/74 MS X 2,948,381 8/1960 Penn 271/74 PG X 3,467,004 9/1969Best et a1. 101/126 X 3,199,447 8/1965 Jaffa et a1. 101/126 X 3,505,9514/1970 Gartrell 101/126 X 3,473,800 10/1969 Nystrand 271/74 FOREIGNPATENTS OR APPLICATIONS 262,053 11/1927 Great Britain 271/74 1,006,217

9/1965 Great Britain 101/126 Primary Examiner-Robert E. PulfreyAssistant ExaminerEugene H. Eickholt Attorney-Robert E. Wagner [57] 1ABSTRACT An improved conveying means for feeding and removing sheetstock to and from a selected area for printing or the like. Theconveying means is inexpensively formed from an endless belt ofmonofilament polyester mesh which moves across a vacuum base disposedbeneath a printing head. The mesh functions as a conveying means and issupported by the vacuum base during printing. The mesh size is fineenough to permit the printing of high quality thin paper stock withoutdiscernible mesh marks appearing after printing is complete. Vacuum isapplied to the underside of the stock to be printed through the meshfrom a known type of vacuum base with sufficient force generated to holdthe sheet stock properly positioned during printing and feeding. Themesh is of the order to from about 140 to 300 threads per inch. Inanother embodiment of the invention, the vacuum belt principle is shownin another form wherein it functions as a take-off conveyor whichfunctions to assist in holding the stock during printing. A smallmanifold function as a belt guide and is all that is required to pullthe stock onto the conveyor.

9 Claims, 5 Drawing Figures VACUUM BELT This invention relates toprinting in general and, more specifically, is directed to a new andimproved conveying means to transport sheet stock such as fabrics, paperand the like into position and hold the same during printing.Thereafter, the conveying means functions to move the printing stock toan area where it may be removed for further processing, packaging or thelike. In a modified form of the invention, a novel belt take-off isprovided, which permits removal of the stock after printing by a novelvacuum belt arrangement which may be used in conjunction with a vacuumbase.

Screen printing oftentimes requires hand feeding of the stock to avacuum bed or flat bed located beneath the printing head. Afterprinting, the stock is removed manually. Attempts have been made toreduce the manual labor in this operation by using a conveyor to movethe printing stock into position during printing. In one form ofconveyor, a plurality of vacuum channels are formed in a vacuum bed anda relatively thick belt is provided with perforations for alignment witheach channel. The stock to be printed is conveyed into position on thebelt for the printing operation. The vacuum is expected to hold itduring printing. In this form of conveying means, the belts are requiredto be specially made to extreme accuracy and alignment of the belt withthe longitudinally extending vacuum groove in an absolute necessity. Asexpected tracking of the belt is critical with very little tolerancegiven. Considerable problems are experienced, particularly from vacuumloss where the belt rides out of the groove. The special manufacturingrequirements of the belt make it costly, thus discouraging widespreadcommercialization. Obviously, the number of grooves and perforations inthe belt are limited and its function as a backing during printing islimited to only certain stocks.

The present invention relates to a novel approach to a solution of theproblem, providing a commercially feasible inexpensive vacuum belt whichis sufficiently thin, permitting it to flex and assume the plane of thebacking plate during the printing operation. In the present invention, avacuum base of known type is provided with an endless belt of stencilscreen material such as a polyester mesh having from about 140 to 300lines per inch. The mesh forms a series of tiny openings functioning asvacuum orifices to hold the sheet stock tightly on the belt duringmovement across the vacuum base. Tracking of' the belt does not requireaccurate alignment as in the prior art designs. Because of the beltquality and mesh size, fine paper stock may be directly printed withoutleaving any mesh marks which are discernible to the unaided eye. Themesh used for the belt is of known type available on the open market,providing the economy desired and thus affording widespread use.

In a second embodiment, the belt is shown in conjunction with a presshaving a vacuum base and functioning as a take-off which assists inholding stock during printing and functions to remove stock at the endof the printing cycle. A narrow vacuum manifold functions to set upvacuum pockets in the mesh as it passes over the manifold. As an option,a vacuum base of known type can also be provided under the centralregion of the take-off conveyor if additional vacuum is needed becauseof the weight of the stock conveyed.

Further advantages of the present invention will become apparent uponconsideration of the objects and novel features set forth hereinafter.

It is an object of this invention to provide a new-and improvedautomated printing system.

It is a further object of this invention to provide a new and improvedconveying means particularly adapted for conveying material to beprinted or the like to a selected area where printing may be performedwith the conveying means functioning as a vacuum holder to hold thestock properly positioned during printing. Where the stock is a textile,ink penetration may be controlled through adjustment of the vacuum.

It is a still further object of this invention to provide a new andimproved conveying means for conveying and holding printing stock.

It is a further object of this invention to provide a new and improvedtake-off conveyor which functions to support and hold the leading edgeof the stock being printed during the printing stroke.

It is a still further object of this invention to provide a novel vacuumbelt take-off, functioning in conjunction with a vacuum base to holdstock during printing and permit expeditious removal thereafter.

It is a still further object of this invention to provide a new andimproved vacuum belt take-off for removal of stock wherein a vacuummanifold only need be provided at the leading or incoming edge of thebelt.

Objects in addition to those specifically stated will become apparentupon reference to the accompanying drawings wherein:

FIG. 1 is a schematic representation of the present invention withcertain details omitted for purposes of clarity;

FIG. 2 is a broken cross-sectional view taken generally along line 22 ofFIG. 1;

FIG. 3 is a greatly enlarged cross-sectional view of the section shownin FIG. 2 with a piece of sheet stock material shown in cross section onthe conveying means;

FIG. 4 is a schematic perspective view of a modified form of theinvention in which the vacuum belt functions as a stock holding andremoval means; and

FIG. 5 is an enlarged cross-sectional view taken generally along thelines 5-5 of FIG. 4.

In FIG. 1, the present invention is illustrated schematically andincludes a screen printing head generally indicated by the referencenumeral 10. The printing head 10 is disposed over a conveying means 11which, in turn, rides over a vacuum bed 12 of any desired length. Aguide rail or stop 18 of known type may be provided at the rear of thebelt. The screen printing head 10 is of known type, consisting of arms13 and 14 supporting a stencil screen 15 which is adapted to be loweredinto engagement with the stock material shown at 16 when it is conveyedbeneath the stencil screen 15. As is well known, a squeegee and floodbar (not shown) force the ink through the stencil openings duringprinting, leaving an imprint on the sheet stock 16 in a known manner.Similarly fixed guides at the front and rear of the belt have not beenincluded in FIG. 1 for purposes of clarity illustrating the invention.

The conveying means 11 transports the sheet stock 16 from an areaoutside the printing area to an area beneath the printing head. Whenprinting is complete, the stock 16 is moved from beneath the head to anarea to the right where it will be removed for further processing,packaging or the like. A modified form of take-off for removal of theprinted stock will be described in conjunction with FIGS. 4 and 5. r

The conveying means 11 is formed from an endless belt 20 which isdisposed around belt supporting rollers 21 and 22. A motor drivearrangement 23 may drive the belt roller 22 through a drive belt 24. Inthe alternative, any type of controllable drive may be used to rotatethe roller 22 through selected increments to provide indexing of thebelt 20, such as a photo cell sensing markings on the edge of a belt oran equivalent form of sensing means.

Referring now to FIG. 2, a vacuum bed of the type shown in acommonly-assigned co-pending application Ser. No. 674,623, DeLuca andBubley, entitled Vacuum Base, now abandoned is illustrated infragmentary broken cross section. The vacuum base 12 consists of a lowerplate 30 and an upper plate 31, the latter being provided with aplurality of perforations 32. The perforations 32 may be symmetricallyarranged or in a random pattern. A honeycomb core 33 forms the center ofthe vacuum bed with a plurality of grooves 34 formed in the lower face35 of the honeycomb core 33. If desired grooves shown in dotted lines 37may be formed on the upper face of the core and function to providecommunication between each of the cells and the source of vacuum.

A conduit 36 is joined to a vacuum source which enables the air to bewithdrawn from the honeycomb bed, drawing air into the ports 32. Thisfunction is more specifically described in the co-pending applicationalluded to above and the disclosure of that application is incorporatedherein by reference. The end wall 38 closes off the space between thelower plate 30 and upper plate 31 to provide an air-tight enclosure withthe exception of the perforations 32. Similar walls are providedcompletely around the vacuum bed. A conduit 36 connects the vacuum bedto any suitable source of vacuum.

Referring now to FIGS. 2 and 3, the endless belt 20 of the conveyingmeans 11 is formed from monofilament polyester material such as ispresently used in stencil screens. The function of this endless belt 20is to convey the sheet material 16 into andout of the printed area whileheld to the belt under the influence of vacuum. While the belt isstopped, the vacuum holds the stock during printing. Backing to opposethe printing force applied to the sheet stock 16 is provided by thevacuum bed 12 with the belt 20 interposed. Quite remarkably, the sheetstock will move the belt across the vacuum bed area, maintaining itsrelative position on the belt due to the influence of the vacuum. Thebelt 20 is easily moved because of the natural lubricity of polyesterwhen moving across a surface of metal, plastic, smooth fiberboard or thelike which may be the material for forming the top laminate or plate 31of the vacuum base 12. In the preferred form, the plate 31 is formed ofa coated aluminum sheet, thus making the vacuum base quite lightweight.

Referring now to FIG. 3, the greatly enlarged crosssectional view showsthe sheet stock 16 to be of comparable thickness to the mesh material20. As indicated by the arrows, air is pulled through the mesh, withfull air flow partially restricted by the size of the mesh 20. Whensheet stock 16 or the like is disposed on the mesh, the air flow isfurther restricted and atmospheric pressure operating on the sheet stockcauses it to be tightly held against the top surface of the belt 20.Fine quality papers may be printed directly on the belt backed by a flatplate without any discernible mesh marks in the final printed product ifthe mesh size is of the order of about threads or lines per inch. It hasbeen found that vacuum is readily pulled through meshes of this size,while meshes in excess of about 300 lines per inch are not sufficientlyporous to provide the requisite holding power. Accordingly, best resultsare obtained with mesh sizes falling between these limits permitting awide range of materials to be printed. A vacuum control of known type isused to control the negative pressure (vacuum). The larger and lessporous the material, the more resistant is the material to vacuum. Theconverse is true for greater porosity.

The vacuum bed 12 may be of any desired size or length, depending uponthe particular requirements. In the embodiment shown, the vacuum bedextends well into the area to the left of the head 10 to permit feedinginto the printing area. The sheet stock 16 may be placed on theconveying means 11 while the preceding sheet (not shown) is beingprinted, thus providing for continuousfeed. Similarly, the sheet stockwill automatically be released on the right-hand end of the conveyingmeans inasmuch as the vacuum bed terminates short of this end,permitting hand or gravity removal. As an alternative, the pressure canbe reversed from negative to positive to effectuate release. If longspans are required, some form of backing may be necessary to support theweight of the sheet stock, however, where it is lightweight paper or thelike, the mesh is sufficiently strong and no additional support isrequired.

It is to be appreciated that the conveying means of the presentinvention may be further provided as optional equipment on a pressequipped with a standard vacuum base which is used to position and holdthe printing stock during printing. With the present form of theinvention, the press may be fed directly from the front and into theprinting position to fixed guides or outside of the printing positionfor greater speed and location of structured obstructions. Most often,the choice will be dictated by the design of the printer and of materialto be printed.

In summarizing the operation, sheet stock 16 may be fed to fixed guidesmounted on the left-hand end to the rear of the belt and vacuum base andthe belt. The motor 23 is energized, causing the sheet stock to beconveyed into position under the screen printing head 10. It iscontemplated that energy to the motor 23 may be controlled through thecircuit controlling the printing head 10 so that it indexes the belt aprescribed increment with each printing. Under head feeding requires noaccuracy. As an alternative, suitable indicia or markings may beprovided on the belt to permit the operator in certain printingoperations to preregister the stock 16 by placing it on prescribedlocations marked directly on the belt. Such indicia or markings may bein the form of grids or lines of known type. Registration may also beobtained by exact indexing of the belt or by feeding to fixed guides.With single color prints, this is not critical as the travel is short.In multicolor operations, special care must be used in registration to acommon or fixed guide as is set forth in copending application Ser. No.826,793, entitled Automatic Multi-Color Printing Arrangement, which isassigned to the assignee of the present invention.

After the printing is complete and the belt 20 moves the following sheetof stock 16 into position under the printing head 10, the precedingsheet of stock will have moved to the area outside the area on the beltlocated beyond the vacuum bed where it may be easily removed. Ifdesired, the sheet stock may be conveyed directly into a dryer or onto arack for drying or to a second station for printing of a diverse coloror the like.

A modified form of the invention is shown in FIG. 4 wherein the vacuumbelt is utilized in a different form to function as a take-off conveyorto remove the stock printed on completion of the printing cycle. Theprinting arrangement is indicated generally by the reference I character110 and includes screen printing heads 111 of conventional design,printing base 112 and take-off conveyor indicated generally at 113.

The printing head 111 functions to position the screen printing frame114 and screen over the stock indicated generally at 115. In the at restposition, the head 111 is in the position shown, however on command,lowers the frame 114 onto the stock 115. Thereafter a squeegee is movedacross the screen to press ink through the stencil screen in a knownmanner. The printing head 111 is elevated to the at rest position shownand the stock is thereafter removed.

The support surface 112 for the stock 115 may consist of a vacuum bed ofthe type described in conjunction with FIG. 1. A guide rail or fixedguide of known type may be provided at the front and/or rear of thevacuum base 112 to permit registration of the stock in a known manner.

With reference to FIG. 5, one form of support or vacuum base 112 isillustrated in cross section with the stock 115 located in the printposition. One end of a squeegee is indicated at 116, the screen frameand screen having been omitted for clarity of illustration. The vacuumbase 112 includes a plurality of openings 117 which permit the drawingof a vacuum within the vacuum base 112 to permit atmospheric pressure toforce the stock 115 into tight engagement with the upper surfacethroughout the printing sequence and connect the vacuum base 112 througha control valve 120 to a source of positive and negative pressure 121.The source of positive and negative pressure may be a turbine-typevacuum pump of known form which permits the application of negative orpositive pressure to the cellular structure in the vacuum base 112through the selective positioning of the valve 120. As indicated by thearrows in FIG. 5, the valve 120 is in the position whereby the negativepressure (vacuum) is applied to hold the stock 115 in position.

This arrangement is similar to the arrangement described in conjunctionwith FIG. 1 and more particularly described in the commonly-assignedco-pending application Ser. No. 674,623 alluded to previously.

The take-off belt 113 includes an endless belt 130 which is disposedaround a drive roller 131 which is driven by a belt 132 from a suitablemotor 133. The belt is also positioned around an idler roller 134 whichis located immediately beneath a manifold 135. The manifold 135 may beof conventional box-beam construction with the ends closed. A pluralityof perforations 136 are provided at spaced intervals adjacent the radiuscorner on the incoming edge of the vacuum belt and function in a mannersimilar to the perforations 117 in the vacuum base 112.

The manifold 135 is connected through a suitable conduit 137 and a valve138 to a source of positive and negative pressure. The round corner onthe box-beam forms a guide to provide a fairly sharp change of directionof the endless belt 130. The manifold 135 is positioned very closelyadjacent the vacuum base 112 and, as illustrated, functions to supportthe leading edge of the stock 115. The vacuum is applied throughout theprinting cycle while the belt 130 is at rest, thus permitting themanifold 135 to apply vacuum to the leading edge of the stock tofunction as a holding and support means during the printing stroke. Atthe conclu-- sion of the printing stroke, the motor 133 is energized andthe endless belt serves to move the printed stock 115 in the directionof the arrow.

In most applications, the vacuum applied through the manifold issufficient to set up small vacuum pockets in the mesh belt 130 and thushold the stock 115 on the belt until such time that it is completelywithdrawn from the printing area. In the event that the stock isheavier, such as cardboard, wood or the like, a second vacuum base maybe provided between the manifold 135 and the drive roller 131 to assurethat the stock will move with the belt. The vacuum base 150 is similarin construction to the vacuum base 112, being connected through asuitable conduit 151 to a source of negative pressure. The vacuum base150 and manifold 135 may be connected to a separate source of vacuum, ifdesired, or a common source.

The belt 130 is formed of monofilament polyester material such aspresently utilized in stencil screens. The belt may include coarse meshsizes as low as 140 threads per inch to fine meshes of about 300 threadsper inch. As is evident, the latter is preferable when fine paper stockare printed. Due to the convenience in fabrication and low cost of thebelt, it is contemplated that various sizes of mesh belts may beavailable for maximum flexibility in printing operations. The belt maybe joined together by a seam formed by overlapping the ends and heatwelding, securing with adhesives or the like. In order to assure thatthe seam is not disposed beneath the stock during printing, a photocellis positioned opposite a light source 161 and a darkened area isprovided on the belt in the region of the seam to assure that the beltwill cycle one full cycle with each operation, thus locating the seam onthe underside of the table.

In the preferred form of the invention, the operation is as follows: Thestock 115 may be loaded onto the vacuum base 112 while no air pressureis applied. The stock may be fed laterally or from the front of thepress to fixed stops or registration guides of known type. Once thestock is positioned, the operator initiates the application of vacuum tohold the stock. The press is also set into operation, causing theprinting head to lower the screen into contact with the stock and causethe squeegee to force ink through the openings onto the stock. At thecompletion of the squeegee stroke, the press head is elevated and, atthis time, through a mechanical switch or the equivalent, the motor 133is energized. Simultaneously with the energization of the motor 133, thenegative pressure which is applied to the vacuum base 112 duringprinting is reversed to a positive pressure or blow back to elevate thestock. Throughout the printing stroke, the manifold 135 has beenmaintained at a negative pressure. As the belt 130 moves, the stock 115will adhere to the belt due to the vacuum set up by the manifold 135through the openings 136. The stock 115 will thus be drawn from theprinting area onto the belt 130 for discharge onto a second conveyorindicated at 160 or placement in a drying rack, or on a belt fortransportation through a dryer. In

the circumstances where the vacuum base 150 is not required, theopenings in the vacuum base may be covered by any suitable means such asa sheet of paper or the like which is taped in place. A positivepressure is applied in the vacuum base 112 to elevate the stock 115 andthus reduce any resistance to movement away from the printing area underthe influence of the vacuum imposed by the manifold 155.

The use of the monofilament polyester material for the belt permits finepaper stocks to be printed without mesh marks appearing, yet the belt isof sufficient strength to effectuate removal of the material once theprinting cycle has been completed. Each opening in the mesh forms avacuum pocket. Moreover, the thinness of the belt permits it to besharply bent at the radiused corner 161, permitting the manifold to bedisposed closely adjacent the right-hand margin of the vacuum base 112.In thicker belt materials, a sharp bend would be impossible to make anda gap between the belt and vacuum base 112 would result.

The registration technique in the embodiment of FIGS. 4 and 5 utilizinga photocell for controlling the stopping of the motor 133 may be usedwith the vacuum belt embodiment shown in FIGS. 1-3. For convenience, thecontrol circuits in each form of the invention have been omitted sinceeach can take various forms utilizing conventional controls and controlcircuits available. Where events are sequenced, as in the lifting andlowering of the press in timed relation to belt movement, the sequenceis controlled by cam-operated switches.

Upon a consideration of the foregoing, it will become obvious to thoseskilled in the art that various modifications may be made withoutdeparting from the invention embodied herein. Therefore, only suchlimitations should be imposed as are indicated by the spirit and scopeof the appended claims.

We claim:

1. An improved conveying means for feeding sheet stock under a printinghead for printing or the like, said printing head being positioned abovesaid conveying means and movable toward and away from a porous printingbed disposed beneath said conveying means, said conveying meanscomprising an endless belt formed of thin polyester woven fabricmaterial having a mesh size from about 140 lines per inch to about 300lines per inch disposed around roller means positioned on opposite sidesof said printing head and said belt projecting beyond opposite sides ofa selected printing area, said belt passing over said porous bed, saidporous bed formed with a plurality of spaced perforations and beingsufficiently rigid to support said stock during printing, means toselectively apply negative pressures to said porous bed, and uniformlythrough said belt to hold said flat stock placed on said belt inposition for printing, and positive pressures to release said flat stockafter printing and means to advance said belt across said porous bed tomove said flat stock under said printing head.

2. In a printing press having a bed to support stock during printingthereon, and a printing head positioned above said bed for movementtoward and away from said bed during a printing operation, theimprovement which comprises a take-off conveyor to remove said stockupon completion of printing, said take-off conveyor including an endlessbelt formed of thin polyester material having a mesh of a size fromabout threads per inch to about 300 threads per inch having an endthereof disposed adjacent an edge of said bed and including means toapply a vacuum through said belt to said stock such that said endsupports and holds a portion of said stock to be printed across theentire leading edge of said stock during the printing thereof.

3. The printing press as defined in claim 2 wherein a vacuum manifold islocated beneath said take-off conveyor in the region of said edge ofsaid stock to be printed.

4. The printing arrangement as defined in claim 2 wherein said bed tosupport said stock during printing includes means to selectively applypositive and negative pressures to the underside of said stock duringprinting and thereby permit holding and removal of said stock,respectively.

5. In combination, a printing press, a porous bed for supporting stockto be printed, and conveying means to assist in holding said stockduring printing and for removal thereof after printing, said meansincluding an endless mesh belt adapted for movement in a direction awayfrom said porous bed, a manifold means disposed under said belt andclosely adjacent a margin of said porous bed, means to apply a negativepressure to said manifold means through said mesh belt thereby to holdsaid stock during printing said mesh belt effecting lateral movement ofsaid stock after printing is complete.

6. The improvement in conveying means as defined in claim 5 wherein saidendless belt is of a mesh size from about 140 lines per inch to about300 lines per inch.

7. The printing arrangement as defined in claim 5 wherein said manifoldmeans is provided with an arcuate edge forming a fixed guide to changethe direction of said mesh belt.

8. The printing arrangement as defined in claim 5 wherein said porousbed for supporting stock during printing includes a means to selectivelyapply negative pressure during printing and positive pressure uponcompletion of printing to permit holding and removal of said stock,respectively.

9. The printing arrangement defined in claim 5 wherein said conveyingmeans to assist in holding and removing said stock includes a vacuumbase adjacent said manifold means and immediately beneath said conveyingmeans to apply additional vacuum to said stock as it is undergoingremoval from the printing area.

t i I I

1. An improved conveying means for feeding sheet stock under a printinghead for printing or the like, said printing head being positioned abovesaid conveying means and movable toward and away from a porous printingbed disposed beneath said conveying means, said conveying meanscomprising an endless belt formed of thin polyester woven fabricmaterial having a mesh size from about 140 lines per inch to about 300lines per inch disposed around roller means positioned on opposite sidesof said printing head and said belt projecting beyond opposite sides ofa selected printing area, said belt passing over said porous bed, saidporous bed formed with a plurality of spaced perforations and beingsufficiently rigid to support said stock during printing, means toselectively apply negative pressures to said porous bed, and uniformlythrough said belt to hold said flat stock placed on said belt inposition for printing, and positive pressures to release said flat stockafter printing and means to advance said belt across said porous bed tomove said flat stock under said printing head.
 2. In a printing presshaving a bed to support stock during printing thereon, and a printinghead positioned above said bed for movement toward and away from saidbed during a printing operation, the improvement which comprises atake-off conveyor to remove said stock upon completion of printing, saidtake-off conveyor including an endless belt formed of thin polyestermaterial having a mesh of a size from about 140 threads per inch toabout 300 threads per inch having an end thereof disposed adjacent anedge of said bed and including means to apply a vacuum through said beltto said stock such that said end supports and holds a portion of saidstock to be printed across the entire leading edge of said stock duringthe printing thereof.
 3. The printing press as defined in claim 2wherein a vacuum manifold is located beneath said take-off conveyor inthe region of said edge of said stock to be printed.
 4. The printingarrangement as defined in claim 2 wherein said bed to support said stockduring printing includes means to selectively apply positive andnegative pressures to the underside of said stock during printing andthereby permit holding and removal of said stock, respectively.
 5. Incombination, a printing press, a porous bed for supportiNg stock to beprinted, and conveying means to assist in holding said stock duringprinting and for removal thereof after printing, said means including anendless mesh belt adapted for movement in a direction away from saidporous bed, a manifold means disposed under said belt and closelyadjacent a margin of said porous bed, means to apply a negative pressureto said manifold means through said mesh belt thereby to hold said stockduring printing said mesh belt effecting lateral movement of said stockafter printing is complete.
 6. The improvement in conveying means asdefined in claim 5 wherein said endless belt is of a mesh size fromabout 140 lines per inch to about 300 lines per inch.
 7. The printingarrangement as defined in claim 5 wherein said manifold means isprovided with an arcuate edge forming a fixed guide to change thedirection of said mesh belt.
 8. The printing arrangement as defined inclaim 5 wherein said porous bed for supporting stock during printingincludes a means to selectively apply negative pressure during printingand positive pressure upon completion of printing to permit holding andremoval of said stock, respectively.
 9. The printing arrangement definedin claim 5 wherein said conveying means to assist in holding andremoving said stock includes a vacuum base adjacent said manifold meansand immediately beneath said conveying means to apply additional vacuumto said stock as it is undergoing removal from the printing area.